An active filter device is connected in parallel to a load such as a power conversion device which generates a harmonic current, and suppresses the harmonic current flowing from the load to a power source (Patent Literature 1). As described in Patent Literature 1, the active filter device includes an inverter unit and a control unit which controls the inverter unit, and the control unit controls the inverter unit so that the inverter unit generates a harmonic current having a phase opposite to the harmonic current generated by the load.